Clubtails are named for the expanded tip of the abdomen in males. Several occur in California, along with related species, including the russet-tipped clubtail, olive clubtail, white-belted ringtail, and gray sanddragon. Compared to the similar russet-tipped clubtail, the brimstone clubtail is smaller, with pale leg bases and a smaller area of dark striping o the thorax.   I took these pictures on an opressively hot, humid August day in the Imperial Valley in extreme southern California.